Development and performance evaluation of supporting arm worn by factory worker for reducing body load

Abstract

This paper proposes a whole mechanism of a supporting arm which is worn by a factory worker for reducing the worker's body load, and performance of the supporting arm was evaluated. The whole mechanism of the supporting arm contains two leg mechanisms for supporting the load and one external frame backpack for connecting the worker's body and the supporting arm. The experimental system of the supporting arm was developed, and its performance was evaluated by several experiments. Firstly, the experimental system was evaluated its capability of supporting a target weight and its controllability of a stiffness characteristic by weightlifting experiments. After that, the supporting arm was worn by two subjects, and its supporting effect was evaluated by measuring electromyogram (EMG) waveforms of leg muscles. When a muscle generates large force, the EMG waveform will also become large. The EMG waveforms are measured by using a four channel surface electromyography, and the worker's leg load will be measured quantitatively. When the worker takes half-sitting posture, its leg load was measured in two cases: (i) a part of the worker's body load is supported by the supporting arm, and (ii) the whole worker's body load is supported only by the worker's legs. The EMG waveforms of these cases were compared, and the supporting effect of the experimental system was validated by t-test. As a result, there is a significant difference between these cases, and EMG waveforms of the case (i) were smaller than that of the case (ii). Therefore, the supporting effect of the supporting arm was demonstrated.

Keywords

• supporting arm
• power assist robot
• factory worker support
• pneumatic cylinder
• support force control
• stiffness control
• electromyogram